Give this a go:
I have just tested it and it is working for me, please not that this is just the satellite imagery, it does not include an overlay of roads or labels.

I don't see any evidence of anyone actively working on Maemo Mapper (particularly the N900 version), so I don't expect a better version to appear any time soon.

With the N900 version of Maemo-Mapper (sorry, can't give the version no. as the About... menu entry displays nothing), the default, OpenStreet map repository, worked well.

Download Sample Repositories... installed several working map repositories, but Google Maps (the one I particularly wanted) was broken. I deleted the installed repositories and re-created Google Maps (see below) and now have a setup, on my N900, with working OpenStreet and Google maps.

Changing between map repositories does not seem to automatically re-draw the current map with the new map, but zooming causes a redraw to the new map.

My working Manage Repositories settings are as follows:

OpenStreet
Google Maps
Simon.